Field of the Invention
The present invention relates to an inkjet printing apparatus which performs printing by ejecting an ink from an ejection port and its control method.
Description of the Related Art
In the inkjet printing apparatus, in a case where a state without ejecting an ink for a long time lasts, moisture in the ink evaporates from the ejection port included in the print head, and ink density increases. In a case where the ink density increases, ink viscosity also increases, and defective ejection can occur easily in ejection. In order to suppress a rise in the ink density caused by defective ejection or moisture evaporation from the ejection port as above, preliminary ejection is performed.
Japanese Patent Laid-Open No. 2000-233518 discloses that the preliminary ejection operation is performed while capping left time or total printing time is short, while a cleaning operation is performed in a case the capping left time or the printing time becomes long depending on a relationship between the capping left time or the total printing time.
Moreover, a lengthy line-type print head in which a plurality of print element substrates are arranged regularly is known, and constitution in which the ink is circulated along an ink channel in the print head with the purpose of suppressing thickening of the ink or discharge of the thickened ink or a foreign substance in the ink is known.
In the constitution of circulating the ink, since fresh ink is supplied to the ejection port at all times, the moisture continuously evaporates from the ejection port during the circulation. Since the moisture evaporates at the ejection port and the thickened ink returns into the circulation path, thickening of the ink in the circulation path gradually advances. Thus, in a case where a degree of thickening in the circulation path has advanced even in the case where the capping left time or the printing time is under the same condition, recovery of an ejection state cannot be complete only with the preliminary ejection operation, and defective ejection occurs.
Moreover, in a case where the cleaning operation is applied uniformly, the ink is wastefully consumed in a case where the degree of thickening in the circulation path has not advanced.